Medical sterilization packaging is needed for storage and transport of various sterilized medical devices. NF EN ISO 11607-1 July 2006 describes in annex A various factors influencing the design of the medical sterilization packaging or medical packaging system using terminology of this standard. Typical sterilization processing is performed by ethylene oxide gas (EO), gamma irradiation (γ), electron beam (e-beam), steam autoclaving, or low-temperature oxidative sterilization processes. If sterilized is to be performed by EO, steam, or oxidizing processes, the packaging is provided with a sterile barrier system that has a permeable component to allow the sterilizing gases to enter, kill the microorganisms, and escape without significant residual concentrations. The sterile barrier system has, in majority of cases, “a top-web”, a “bottom web”, and a means to join the webs together. In the case where a peelable seal is required, a sealant layer is applied to allow sealing of the two layers together. The sealant layer, typically produced by off-line coating, has traditionally been applied to the permeable web. Today, many films incorporate the sealant layer as (a) layer(s) in the film construction. Where a weld seal is required, compatibility of the webs is required to allow joining by heat or pressure.
The sterile barrier system porous web is often made of medical paper that is manufactured to be free of contaminants or micro-organisms and that has been processed to close large pores that could pass micro-organisms while leaving sufficient permeability for the sterilisation agents such as the EO gas. Medical papers should meet predetermined minimum physical requirements such as air permeance, tensile strength, tear resistance, and burst strength. Various other requirements are also set in paragraphs 5.1.7 and 5.1.9 of the aforementioned ISO standard. The latter paragraph sets requirements for the sealing if any is formed and for the peel-open characteristics. The peel-open shall be continuous and homogenous without delamination or tearing of the material that can affect aseptic opening and presentation. Other requirements such as microbial barrier properties are also defined by the ISO standard in question.
Sealable and peelable medical paper for medical sterilization packaging are produced using off-line or on-line processing. On-line processing removes the need for a subsequent process step and saves energy while adding complexities and particular requirements for reliability of the processing to avoid producing of waste and consuming energy. For example, WO0231248 (A2) discloses a method of producing such paper by impregnating or saturating the paper web by mixing in the pulp a composition comprising a drapable saturant component and an additional saturant polymer. The composition should provide an enhanced seal strength between the fibrous web and a base component polymeric material. By saturating the paper it is desired to enable sealing directly to materials used in the base components of the paper web so that separate off-line coating is not needed. The saturating of the paper with such compositions yet consumes relatively large amounts of technical chemicals that are more expensive than the normal source materials of paper. Moreover, such polymers may be produced from oil and hinder recycling of the paper for production of other grades of paper or board with commercially applicable paper recycling technologies.
Off-line coating based methods may provide more efficient use of renewing natural materials. In one technique, instead of pulp additive based impregnation, a paper web in a paper machine is first formed, dried and on-line sized by applying some binder with a size press on both sides of the paper web as the size press on operation forms a pond of the binder material on both sides of the web and these ponds mix freely at both edges of the web. The paper web is then dried and rolled into machine rolls. Subsequently, a heat sealing layer is off-line coated onto the paper web. The on-line application of the binder helps to avoid tear, so releasing of fibres, especially cellulosic material that can affect the aseptic opening and presentation of packaged medical objects, as the heat-sealing layer is formed onto a reinforcing material layer. The peeling occurs within the heat-sealing layer and/or on the interface between the heat-sealing layer and the reinforcing material layer. It is yet desirable to avoid the off-line coating as a relatively expensive procedure.
One known technique for forming peelable medical papers for medical sterilized packaging applies the heat-sealing layer onto the paper web by using off-line extrusion of polyethylene.
An object of the invention is to provide ecological and economical sealable and peelable medical paper for medical sterilization packaging and packaging containing same, to eliminate or mitigate some drawbacks relating to prior known such papers and packages and the production of the same, or to provide a new technical alternative.